Absorbing nonwoven materials are often used for wiping spills and leakages of all kinds in industrial, service, office and home locations. There are great demands on the properties of nonwoven materials made for wiping purposes. An ideal wiper should be strong, absorbent, abrasion resistant and exhibit low linting. It should further be soft and have a textile touch. Hydroentangled nonwoven materials are often used as wipes because of their absorbent and textile-like properties.
Hydroentangling or spunlacing is a technique introduced during the 1970′ies, see eg CA patent no. 841 938. The method involves forming a fibre web which is either drylaid or wetlaid, after which the fibres are entangled by means of very fine water jets under high pressure. Several rows of water jets are directed against the fibre web which is supported by a movable fabric. The entangled fibre web is then dried. The fibres that are used in the material can be synthetic or regenerated staple fibres, eg polyester, polyamide, polypropylene, rayon or the like, pulp fibres or mixtures of pulp fibres and staple fibres. Spunlace materials can be produced in high quality to a reasonable cost and have a high absorption capacity. They can eg be used as wiping material for household or industrial use, as disposable materials in medical care and for hygiene purposes etc.
Through eg EP-B-0 333 211 and EP-B-0 333 228 it is known to hydroentangle a fibre mixture in which one of the fibre components consists of continuous filaments in the form of meltblown fibres. The base material, ie the fibrous material which is exerted to hydroentangling, either consists of at least two combined preformed fibrous layers where at least one of the layers is composed of meltblown fibres, or of a “coform material” where an essentially homogeneous mixture of meltblown fibres and other fibres is airlaid on a forming fabric.
Through EP-A-0 308 320 it is known to bring together a prebonded web of continuous filaments with a separately prebonded wetlaid fibrous web containing pulp fibres and staple fibres and hydroentangle together the separately formed fibrous webs to a laminate. In such a material the fibres of the different fibrous webs will not be integrated with each other since the fibres already prior to the hydroentangling are bonded to each other and only have a very limited mobility. The material will show a marked twosidedness.
WO 99/22059 discloses a method of producing a nonwoven material by hydroentangling a mixture of continuous filaments, natural fibers and/or synthetic staple fibers. A fibrous web of natural fibers and/or synthetic staple fibers is foamformed and hydroentangled and integrated with the continuous filaments, for example meltblown fibers.
WO 2005/042819 discloses a method of producing a nonwoven material by forming a web of continuous filaments on a forming fabric and applying a wet-formed fibre dispersion containing synthetic staple fibres having a length between 3 and 7 mm, and natural fibres on top of said continuous filaments. The fibrous web is subsequently hydroentangled to form a nonwoven material.
One problem is clearly seen in hydroentangled materials—they will very often be markedly twosided, ie it can clearly be discerned a difference between the side facing the fabric and the side facing the water jets in the entangling step. In some cases this has been used as a favourable pattern, but in most cases it is seen as a disadvantage. When two separate layers are combined and fed into an entangling process, normally this process step cannot thoroughly mix the layers, but they will still exist, albeit bonded to each other. With pulp in the composite there will be a pulp-rich side and a pulp-poor side, which will result in differing properties of the two sides. This is pronounced when spunlaid filaments are used as they tend to form a flat two-dimensional layer when created, which will mix poorly.
It is further known to make a material having the same fiber composition on both sides, wherein in a first step a hydroentangled nonwoven material is produced comprising a mixture of pulp fibers and synthetic staple fibers, said mixture being wetlaid on top of a web of spunlaid filaments. In a second step said hydroentangled nonwoven material is fed back into the process and a second mixture of pulp fibers and synthetic staple fibers is wetlaid on top of the hydroentangled nonwoven. The combined fibrous layers are then hydroentangled. This is a costly, time consuming and energy demanding process which does not fully solve the problem.